Data structure - parent

This is a discussion on Data structure - parent within the Windows Programming forums, part of the Platform Specific Boards category; I'm making a GUI application and it's 'front-ended' around a 5MB data structure.
My application has an MDI frame as ...

I tried making it a member of the main frame's class, initializing the structure in the frame's constructor, but when I did the program would either crash or when I started the program I'd get no visual. It would appear for half a second in the task manager, then disappear. However, when I make it part of the main program's class and initialize it in the OnInit() function (I'm using wxWidgets instead of VC++ - works about the same), it works and I have no problems.